1. Field of the Invention
The present invention relates to a method of improving a winding shape of a coil to be wound by a down coiler by hydraulic pinch rolls controlled by a hydraulic cylinder and a servo valve and to a control unit thereof.
2. Description of the Related Art
FIG. 1 shows pinch rolls 1, including upper pinch roll 1a and lower pinch roll 1b, of a down coiler 2 of hot rolling equipment being a subject of the present invention. In the hot rolling equipment, a strip 4 that has been rolled to a predetermined plate thickness by a finishing mill 3 is rolled by the down coiler to be an end item in a coil state. The pinch rolls 1a, 1b function to guide a strip 4 run on a table roller 5 to the down coiler 2.
Recently, as shown in FIG. 2, a hydraulic pinch roll that controls the position of upper and lower pinch rolls and a pressing force to the strip by a hydraulic cylinder 6 and a servo valve 7 has been commercialized. Function required to such pinch rolls 1 is stretching the strip 4 to guide to the down coiler 2 in an initial period of the winding and stretching the strip 4 in an opposite direction to maintain an appropriate tension with a mandrel 2e after the strip 4 has been wound to the mandrel 2e. Accordingly, an appropriate force is given to the pinch rolls 1 to press the strip 4.
The hydraulic pinch rolls 1 shown in FIG. 2 is constituted as follows. Specifically, right/left chucks 1c and 1d of an upper pinch roll 1a is supported by the hydraulic cylinder 6 and control of excurrent/incurrent of oil to the hydraulic cylinder 6 is performed by the servo valve 7 connected via piping 8a and 8b. Pressure detector 9a and 9b are severally connected to the piping 8a and 8b so that the pressure of the hydraulic cylinder 6 at a head side 6a and a rod side 6b can be detected. Moreover, position detectors 10c and 10d can detect the position of a piston 6c of the hydraulic cylinder 6.
In the hydraulic pinch rolls 1, an initial gap is set by detecting the position of the piston 6c of the hydraulic cylinder 6 by the position detectors 10c and 10d and by controlling the position of the upper pinch roll 1a based on the signal of the detection. After the strip 4 bounces into the pinch rolls 1 to be guided to the down coiler 2, a positional control is switched to a pressing force control in an appropriate timing, and a pressing force arithmetical unit 11 calculates the pressing force to the strip 4 of the upper pinch roll 1a based on the pressure of the head and rod sides 6a and 6b, which has been detected by the pressure detectors 9a and 9b, and then a servo controller 12 sends an instruction to a servo valve 7 based on the signal of the calculation to control the pressing force.
In a conventional down coiler 2, a defective winding shape of the coil (a telescope), as shown in FIG. 3, has occurred due to reasons such as the case where a plane shape of the strip 4 to be wound is bad and where the strip 4 enters the pinch rolls 1 in an off-center manner. Furthermore, recently, when a wide and hard material is wound, a problem of multiple defective winding shapes as shown in FIG. 4 in which an end surface of a wound coil has an iterative unevenness.
In consideration of the foregoing circumstances, the object of the present invention is to provide a control method of the hydraulic pinch rolls that can suppress the defective winding shape and a control unit thereof.
The inventor of the present invention has found out that the right/left difference of a piston position of the hydraulic pinch rolls, that is, the output difference of the position detectors 10c and 10d shows a periodic fluctuation when the defective winding shape occurs where the end surface of the wound coil has an iterative unevenness, and that the output difference does not show the periodic fluctuation when the defective winding shape does not occur.
Accordingly, in a first embodiment of the present invention, the control unit of the hydraulic pinch rolls is constituted such that the pressing force of the right and the left of the pinch rolls is changed moment by moment in accordance with the output difference of the position detectors 10c and 10d and the fluctuation shown in the output difference of the position detectors 10c and 10d can be suppressed. As a result, a gap fluctuation that occurs alternately in right and left (a seesaw state) on the upper pinch roll 1a of the hydraulic pinch rolls 1 can be prevented.
In a second embodiment of the present invention, since the control unit of the hydraulic pinch rolls 1 changes the gaps of the right and left of the pinch rolls by positional control moment by moment in accordance with the pressing force of the pinch rolls obtained from the output of the pressure detectors 9a and 9b, the gap of the pinch rolls is maintained parallelly. Accordingly, the gap fluctuation that occurs alternately in right and left on the upper pinch roll 1a can be prevented. As a result, the defective winding shape where the end surface of a wound coil iterates the periodical unevenness can be prevented.
Other objects and advantageous characteristic of the present invention will be made clear by the following description with reference to the accompanied drawings.